The baby was treated for a broken leg and Crossman, 24, of Orono is standing trial for felony aggravated assault. If convicted, she faces up to 10 years in prison and a fine of up to $20,000.

Her son “Eric David starting crying. She couldn’t get him to stop crying,” the former detective, who now works for Penobscot County Sheriff’s Department, said of the baby. “She was very upset.”

While telling the detective her story, Crossman used an open palm to strike her leg repeatedly, Whitehouse said, giving the jury a physical demonstration of her action.

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Striking the 9-month-old “did not stop the baby from crying,” the detective said, adding that Crossman told the officer she was so mad she had to leave the room.

Crossman was on the phone with her parents, who live out of state, and she was arguing with them over money, Whitehouse said.

The baby was taken to the emergency room at Eastern Maine Medical Center in Bangor on Nov. 6, 2010, with a broken left femur and bruising, including hand prints that are a “classic injury” in child abuse cases, Dr. Kathryn Ruthledge testified.

The baby’s mother initially said he rolled off a bed two days beforehand, which was not consistent with his injuries, said Ruthledge, who is an EMMC pediatric hospitalist, a specialist called in whenever a child abuse case is suspected for children under the age of 21 months.

Crossman changed her story when confronted by Whitehouse.

In addition to police, a representative from the Department of Health and Human Services was called and the baby initially was placed in the agency’s custody when Crossman was charged, Orono police Capt. Josh Ewing said at the time of her arrest.

Defense Attorney Stephen Smith asked that all references to the ongoing DHHS case not be admitted, which was agreed upon by Superior Court Justice John Nivison, who is hearing the trial.

The case is being tried at the Penobscot Judicial Center in Bangor and is expected to end Tuesday after the state calls Dr. Lawrence “Larry” Ricci of Portland, who is considered one of the state’s foremost medical experts on child abuse.

Where the baby, now just over 2 years of age, and his older brother, who is around 3 ½ years old, are now living was not released during Monday’s trial and was something Assistant District Attorney Alice Clifford, who is prosecuting the case, declined to discuss after Monday’s afternoon court session was over.

Monday’s morning session ended with Smith grilling Whitehouse about why the detective didn’t interview Crossman’s numerous roommates or the father of the baby until after she was arrested.

Whitehouse said “given the confession and the demonstration [by Crossman]” and “the injury that was reported at the hospital,” the detective said he felt confident in arresting Crossman for aggravated assault.

Crossman told Ruthledge there was nothing wrong with her son when she put him to bed at around 6 p.m. on Nov. 5, 2010, or when he woke up at around 7:30 a.m. and was changed and given a bottle and went back to sleep. It was at around 11:30 a.m. on Nov. 6, 2010 that Crossman first noticed swelling on her son’s small leg and called a relative who is an emergency medical technician, Ruthledge told jurors.

When Eric David’s father got home from work, Crossman informed him of the leg swelling and went off to work but she wasn’t there long because the boy’s father called about an hour into her shift saying their child had to go to the hospital, Ruthledge and Whitehouse said, recalling what Crossman told them.

When Whitehouse told Crossman the evidence didn’t match her story, “I asked her if anything else happened,” the detective said. “I noticed she started to become upset. Her eyes started to swell with tears.”

After telling Whitehouse about the argument with her parents, “she indicated to me she hit him in the leg.”

When Whitehouse placed Crossman into handcuffs, Catherine Dawson, a social worker who was in the same room, heard the mother say she was confused.

“She said she didn’t understand because she only hit him a couple times,” the social worker said.